The prior art reciprocating hermetic compressors are, as a rule, provided with suction acoustic dampening systems (acoustic filters) inside the shell, with the function of attenuating the noise generated during the suction of the refrigerant fluid.
One of the causes which reduces the efficiency of the compressors using the present acoustic mufflers is the overheating of the gas being drawn. During the time elapsed between the entrance to the compressor and the admission into the cylinder thereof, the gas temperature is increased, due to the heat transferred from the several hot sources existing inside the compressor. The temperature increase causes an increase in the specific volume and consequently a reduction of the refrigerant mass flow. Since the refrigerating capacity of the compressor is directly proportional to the mass flow, reducing said flow results in efficiency loss.
It is well known that the thermal insulation of the gas being drawn by a hermetic compressor during its travel inside the hermetic shell of said compressor, from the suction inlet tube to the suction orifice, has a significant effect in relation to the increase of the refrigerating capacity and compressor efficiency. Among the means used to provide the thermal insulation, the more effective one is the use of an acoustic muffler in the form of a suction chamber of plastic material, provided with a tube to conduct gas from within the hermetic shell towards the suction orifice in the cylinder head. Said muffler, when the assembly is mounted, is suspended in relation to the body of said chamber (U.S. Pat. No. 4,755,108). The distribution of volumes and tubes and respective openings in the acoustic muffler is what characterizes, acoustically, the dampening effect of the noise generated in the gas suction. In order that the noise be dampened, the tube which conducts the gas to the suction chamber should be provided with openings communicating the inside of said tube with the internal volumes of the muffler. It is thus characterized, in the same assembly, a sequence of tubes disposed in series. The various tube sections are disposed in such a way as to provide a direction of the gas being drawn, avoiding the mixture of this cooler gas being drawn with the hotter gas found inside the chamber volumes.
In one known solution (U.S. Pat. No. 4,755,108), the construction of the acoustic muffler allows small leaks to occur in the connections of the two parts that normally form the tube. Said leaks, in more serious cases, substantially reduce the muffler efficiency in acoustic terms. There is also an additional complication related to the manufacturing process, owing both to the number of pieces involved (usually four) and to the usually more complex geometry of said pieces, resulting from the little space available inside the hermetic shell of the compressor.
One way used to overcome such deficiency, also known in the prior art (U.S. Pat. No. 4,960,368) is based on the configuration of the tubes and volumes defined in the muffler body, which reduces the number of pieces, without impairing the acoustic characteristic of the muffler. Nevertheless, in this solution there is some loss in the performance related to the heat conducted from the muffler body to the gas. This occurs as a function of the contiguity of the faces of the tube which conducts the gas to the cylinder with the internal invironment of the compressor, which is at a higher temperature.